Rotary machine

ABSTRACT

Provided is a rotary machine including: a shaft that rotates; a disc that has a substantially cylindrical hub fitted into the shaft and is provided so as to widen outward in a radial direction from a front end to a rear end of the hub; and an impeller having a plurality of blades provided on a surface of the disc. The hub has a tight fit section having an internal radius that is smaller than a radius of the shaft, and a loose fit section having an internal radius that is greater than the internal radius of the tight fit section. The loose fit section is provided on the front end side of the hub with respect to the tight fit section.

TECHNICAL FIELD

The present invention relates to a rotary machine with which an impelleris equipped.

This application claims priority to and the benefit of Japanese PatentApplication No. 2010-273589 filed on Dec. 8, 2010, the disclosure ofwhich is incorporated herein by reference.

BACKGROUND ART

A centrifugal compressor used for a rotary machine such as an industrialcompressor, a turbo refrigerator, and a small gas turbine includes animpeller provided with a plurality of blades on a disc fixed to a shaft.The centrifugal compressor gives pressure energy and speed energy to agas by rotating the impeller.

FIG. 6 is an explanatory view of a rotary machine of the related artthat includes an impeller 201.

For example, a rotary machine of PTL 1 includes the impeller 201constituted by a disc 203, a blade 204, and a cover 206. At apredetermined position of the impeller 201 in an axial direction, asleeve portion 205 is formed integrally with the impeller 201. Byperforming shrinkage-fitting of the sleeve portion 205 to the shaft 202at the predetermined position, the impeller 201 is fixed to the shaft202.

PTL 1 discloses that when an internal radius of the sleeve portion 205is set to R and a thickness in the range of the length L is set to T,the length L in which the centrifugal force of the impeller 201 does notaffect the sleeve portion 205 is expressed by the following expression(1).

[Expression 1]

L≧1.8√{square root over (RT)}  (1)

That is, PTL 1 discloses that the influence of the radial displacementof the inner diameter of the impeller 201 due to the centrifugal forceduring rotation to the sleeve portion 205 is suppressed by setting thelength L so as to satisfy the expression (1), and the stable operationis maintained without deviation of the impeller 201 and the shaft 202.

CITATION LIST Patent Literature

-   [PTL 1] U.S. Pat. No. 4,697,987

SUMMARY OF INVENTION Technical Problem

In general, the cover 206, the blade 204, and the disc 203 are molded asindividual components, and then the blade 204 and the cover 206 aremounted on the disc 203 by welding or the like.

In the case of the impeller 201 of PTL 1, the sleeve portion 205 isplaced at a position separated from an inner circumferential portion Bof the disc 203 by a length L so as to satisfy the expression (1). Thatis, the sleeve portion 205 is placed so as to project to the side of thedisc 203 in the axial direction on which the blade 204 and the cover 206are mounted.

For this reason, when the blade 204 and the cover 206 are mounted on thedisc 203 by welding or the like, there is a problem in that the sleeveportion 205 projecting from the disc 203 is obstructive, and workabilityis degraded.

Furthermore, the centrifugal compressor used for the rotary machine ofrecent years requires an improvement in performance such as a highoutput and a high rotation.

In general, the center of a half section of the impeller 201 of PTL 1 isplaced on the disc 203 side that is provided with the blade 204, thecover 206 or the like. That is, the center of the half section of theimpeller 201 is placed at the position that is greatly separated fromthe sleeve portion 205.

According to PTL 1, by placing the sleeve portion 205 so as to beseparated by the length L, it is possible to suppress the radialdisplacement of the impeller 201 due to the centrifugal force affectingthe sleeve portion 205.

However, since the center of the half section of the impeller 201 isgreatly separated from the sleeve portion 205, the sleeve portion 205easily extends outward in the radial direction due to the centrifugalforce of the impeller 201. Particularly, as output and rotation of theimpeller 201 become higher, there is a concern that the influence of theradial displacement of the impeller 201 may not be suppressible. Thus,there is a risk of the sleeve portion 205 widening, deviation occurringbetween the impeller 201 and the shaft 202, and the performance of therotary machine deteriorating.

Thus, the present invention is made in view of the above-mentionedcircumstances, and an object thereof is to provide a rotary machine thathas satisfactory workability during manufacturing, and is capable ofsuppressing the deviation between the impeller and the shaft at the timeof rotation.

Solution to Problem

In order to achieve the above-mentioned object, according to the presentinvention, there is provided a rotary machine that includes a shaft thatrotates; a disc that has a substantially cylindrical hub fitted into theshaft and is provided so as to widen outward in a radial direction froma front end to a rear end of the hub; and an impeller having a pluralityof blades provided on a surface of the disc, wherein the hub has a tightfit section having an internal radius smaller than a radius of theshaft, and a loose fit section having an internal radius greater thanthe internal radius of the tight fit section, and the loose fit sectionis provided on the front end side of the hub with respect to the tightfit section.

According to the present invention, the blade is provided on the surfaceof the disc, and the hub is provided without projecting from the surfaceof the disc. For this reason, when the blade is mounted on the surfaceof the disc, the hub is not obstructive. Thus, it is possible to providethe rotary machine having satisfactory workability at the time ofmanufacturing.

Furthermore, in PTL 1, since the sleeve portion fitted into the shaft isplaced so as to be separated from the center of the half section of theimpeller, a structure in which the sleeve easily widens outward in theradial direction is provided. However, according to the presentinvention, the hub is provided so that a part thereof projects from therear surface of the disc, and the tight fit section having the greattightening allowance is provided on the rear end side of the hub. Thatis, the hub is provided near the center of the half section of theimpeller, and the tight fit section provided in the hub is fixedlyfitted into the shaft. Thus, it is possible to prevent the tight fitsection from widening due to the centrifugal force at the time ofrotation, and the deviation between the impeller and the shaft can besuppressed.

In the rotary machine of the present invention, a groove portion dentedso as to surround the hub may be provided on the rear surface of thesurface of the disc.

In this case, by providing the groove portion around the hub on the rearsurface of the disc, it is possible to suppress the tight fit sectionfrom widening outward in the radial direction due to the centrifugalforce at the time of rotation, and the contact pressure of the tight fitsection can be maintained. Thus, it is possible to reliably suppress thedeviation between the impeller and the shaft at the time of rotation.

In addition, the thick portion of the disc can be removed by providingthe groove portion, and the thickness difference of each portion of thedisc can be reduced. Thus, for example, when enhancing the strength ofthe disc by quenching, annealing or the like, the entire disc can beevenly heat-treated. Thus, it is possible to provide the rotary machineof high performance having excellent strength.

In the rotary machine of the present invention, a first tapered portionhaving an external radius gradually increasing toward the front end ofthe hub may be provided in the rear end of the hub.

For example, in some cases, shortening of the length of the tight fitsection may be required due to the circumstances such as the layout ofthe impeller. In this case, in order to supplement the reduction of thecontact pressure due to shortening of the tight fit section, there is aneed to increase the thickness of the tight fit section. However, whenthe thickness of the tight fit section is increased, there is a risk ofthe thick portion being pulled outward in the radial direction due tothe centrifugal force, the tight fit section widening outward in theradial direction, and deviation occurring between the impeller and theshaft.

However, according to the present invention, it is possible to suppressthe tight fit section from widening outward in the radial direction dueto the centrifugal force, by providing the first tapered portion in therear end of the hub. Thus, by providing the first tapered portion, it ispossible to shorten the length of the tight fit section, while reliablysuppressing the deviation between the impeller and the shaft at the timeof rotation, and provide a small impeller.

In the rotary machine of the present invention, a sleeve, which isfitted into the shaft so as to come into contact with the front end ofthe hub and guides the air flow to the disc, may be further included.

In this case, the air flow can be effectively guided by placing thesleeve. In addition, by individually providing the disc and the sleeve,after mounting a blade or the like on the surface of the disc, thesleeve can be placed on the front end of the hub. Thus, when the bladeor the like is mounted on the surface of the disc, the sleeve is notobstructive. Thus, it is possible to provide the rotary machine that hassatisfactory workability at the time of manufacturing.

In the rotary machine of the present invention, the plurality ofimpellers may be provided in series in the shaft, a sleeve that guidesthe air flow to the disc of the other impeller may be further includedbetween the hub of one impeller and another hub of another impelleradjacent thereto, and a second tapered portion having an internal radiusgradually decreasing toward the rear end of the sleeve so as to bematched with a shape of the first tapered portion provided in the rearend of the hub may be provided in the front end of the sleeve.

In this case, since the second tapered portion matched with the shape ofthe first tapered portion is provided in the front end of the sleeve,the sleeve can be placed in the state in which the second taperedportion is brought into contact with the first tapered portion. Thereby,since the second tapered portion is able to press the first taperedportion from the outside in the radial direction, it is possible tosuppress the tight fit section from widening outward in the radialdirection due to the centrifugal force. Thus, it is possible to reliablysuppress deviation between the impeller and the shaft at the time ofrotation.

In the rotary machine of the present invention, a concave portion may beprovided in any one of the rear end of the sleeve and the front end ofthe hub, and a convex portion matched with the shape of the concaveportion may be provided in the other thereof.

In this case, since it is possible to perform the concave and convexfitting of the rear end of the sleeve and the loose fit section, themovement of the loose fit section can be restricted by the sleeve, andit is possible to suppress the loose fit section from widening outwardin the radial direction due to the centrifugal force. Thus, it ispossible to reliably suppress the deviation between the impeller and theshaft at the time of rotation.

In the rotary machine of the present invention, a third tapered portionhaving an internal radius gradually decreasing toward the front end ofthe sleeve may be provided in the rear end of the sleeve, and a fourthtapered portion having an external radius gradually decreasing towardthe front end of the hub so as to be matched with the shape of the thirdtapered portion may be provided in the front end of the hub.

In this case, the third tapered portion is provided in the rear end ofthe sleeve. In addition, the fourth tapered portion having the shapematched with the shape of the third tapered portion is provided in thefront end of the hub. For this reason, the sleeve can be placed in thestate in which the third tapered portion is brought into contact withthe fourth tapered portion. Thereby, since the third tapered portion isable to press the fourth tapered portion from the outside in the radialdirection, it is possible to suppress the loose fit section fromwidening outward in the radial direction due to the centrifugal force.Thus, it is possible to reliably suppress the deviation between theimpeller and the shaft at the time of rotation.

In the rotary machine of the present invention, the tight fit sectionmay be provided over the front end side with respect to the rear surfaceof the disc from the rear end of the hub.

In this case, by providing the tight fit section over the front end sidewith respect to the rear surface of the disc, it is possible to providethe tight fit section at the position that is closer to the center ofthe half section of the impeller. Thus, it is possible to suppress thedeviation between the impeller and the shaft at the time of rotation.

In the rotary machine of the present invention, the hub may further havean intermediate section that connects the tight fit section with theloose fit section.

According to the present invention, by placing the intermediate sectionbetween the tight fit section and the loose fit section, the tight fitsection is fitted into the shaft at the position separated from the rearsurface of the disc to the rear end side of the hub. Thereby, even whenthe disc widens outward in the radial direction due to the centrifugalforce, the intermediate section bends, and the influence on the tightfit section can be relaxed. Thus, since it is possible to suppress thetight fit section from widening outward in the radial direction due tothe centrifugal force, it is possible to suppress the deviation betweenthe impeller and the shaft at the time of rotation.

Advantageous Effects of Invention

According to the rotary machine of the present invention, when the bladeis mounted on the surface of the disc, the hub is not obstructive, andworkability is satisfactory at the time of manufacturing.

Furthermore, according to the rotary machine of the present invention,the tight fit section provided in the hub of the impeller is fixedlyfitted into the shaft, it is possible to prevent the tight fit sectionfrom widening due to the centrifugal force at the time of the rotation,and it is possible to reliably suppress the deviation between theimpeller and the shaft at the time of rotation.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an explanatory view of a centrifugal compressor to which arotary machine of the present invention is applied.

FIG. 2 is an explanatory view of the rotary machine when viewed from anaxial direction.

FIG. 3 is a cross-sectional view taken along line A-A of FIG. 2 and anexplanatory view of the rotary machine of a first embodiment.

FIG. 4 is an explanatory view of a rotary machine of a secondembodiment.

FIG. 5 is an explanatory view of a rotary machine of a third embodiment.

FIG. 6 is an explanatory view of a rotary machine of the related art.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present invention will be described withreference to the drawings.

(Centrifugal Compressor)

FIG. 1 is an explanatory view of a centrifugal compressor 100 to which arotary machine 1 of the present invention is applied.

The centrifugal compressor 100 mainly includes a shaft 5 rotating aroundan axis O, an impeller 10 that is attached to the shaft 5 and compressesa gas G using the centrifugal force, and a casing 105 that rotatablysupports the shaft 5 and forms a flow path 104 causing the gas G to flowfrom an upstream to a downstream. In addition, in the illustratedexample, although six impellers 10 are provided in series in the shaft5, at least one impeller 10 may be provided in the shaft 5.

An outer appearance of the casing 105 is formed in an approximatelycolumnar shape, and the shaft 5 is placed so as to penetrate through thecenter thereof. On both ends of the shaft 5 in the axial direction, ajournal bearing 105 a is provided. Furthermore, a thrust bearing 105 bis provided in one end of the shaft 5. The shaft 5 is rotatablysupported by the journal bearing 105 a and the thrust bearing 105 b.Thereby, the shaft 5 is supported by the casing 105 via the journalbearing 105 a and the thrust bearing 105 b.

On one side (a left side in FIG. 1) of the casing 105 in the axialdirection, an inlet port 105 c which causes the gas G to flow in fromthe outside is provided. Furthermore, on the other side (a right side inFIG. 1) in the axial direction, an outlet port 105 d through which thegas G flows to the outside is provided.

In the casing 105, an internal space that communicates with the inletport 105 c and the outlet port 105 d and repeats the diameter reductionand the diameter expansion is provided. The internal space is used as aspace that accommodates the impeller 10, and also serves as the flowpath 104. That is, the inlet port 105 c and the outlet port 105 dcommunicate with each other via the impeller 10 and the flow path 104.

(Rotary Machine of First Embodiment)

Next, the rotary machine 1 of the first embodiment will be described.

FIG. 2 is an explanatory view of the rotary machine 1 of the firstembodiment when viewed from an axial direction.

FIG. 3 is a cross-sectional view taken along line A-A of FIG. 2, and anexplanatory view of the rotary machine 1 of the first embodiment.

In addition, in the following description, in order to simplify thedescription, in some cases, the upstream side (corresponding to “frontend side” of the claims, and the left side in FIG. 2) of the gas Gflowing through the centrifugal compressor 100 is simply referred to asa front side, and the downstream side (corresponding to “rear end side”of the claims, the right side in FIG. 2) is simply referred to as a rearside. Furthermore, in order to simplify the description, a case in whichthe shaft 5 is provided with one impeller 10 will be described.

(Disc)

The rotary machine 1 illustrated in FIG. 2 includes an impeller 10. Theimpeller 10 has a disc 12, a plurality of blades 14 provided in the disc12, and a cover 16 placed so as to be separated from the disc 12 by apredetermined distance.

For example, the disc 12 is formed by precipitation hardening stainlesssteel, and is a disk-like member having an approximately circular shapewhen viewed from the axial direction.

The disc 12 has an external diameter that gradually widens from thefront side toward the rear side (from the left side to the right side inFIG. 2). A front side surface 12 a (surface) of the disc 12 is formed ina curved state when viewed from the cross section in the radialdirection. The front side surface 12 a formed in the curved state isconfigured so that a surface located inside in the radial direction isformed along the axis O and formed so as to gradually follow the radialdirection as it moves outward in the radial direction. Moreover, a blade14 to be described later is attached to the front side surface 12 a ofthe disc 12.

Furthermore, the rear side surface 12 b (rear surface) of the disc 12 isflatly formed. In addition, as will be described later, a groove portion18 is provided on the rear side surface 12 b of the disc 12.

A hub 20 fitted into the shaft 5 is provided inside the disc 12 in theradial direction. That is, the disc 12 has the substantially cylindricalhub 20 fitted into the shaft 5. The disc 12 is fitted into the shaft 5so as to widen outward in the radial direction from the front end of thehub 20 toward the rear end thereof. A part of the hub 20 protrudes fromthe rear side surface 12 b of the disc 12. The hub 20 has a through holethat penetrates through the front side and the rear side of the disc 12.The hub 20 has a tight fit section 22 and a loose fit section 24.

The tight fit section 22 has a thickness T1 in the radial direction, anda length L1 from the rear side to the front side (from the right side tothe left side in FIG. 2). In addition, the tight fit section 22 isprovided over the front side from the rear side surface 12 b of the disc12.

An internal radius R of the tight fit section 22 is set to be smallerthan the radius of the shaft 5. Moreover, for example, the tight fitsection 22 is fitted into the shaft 5 by shrinkage-fitting or the like.

Herein, the length L1 of the tight fit section 22 in the axialdirection, the thickness T1 of the tight fit section 22, and theinternal radius R of the tight fit section 22 are set so as to satisfythe following expression (2).

[Expression 2]

L1/√{square root over (RT1)}≧0.8˜0.9  (2)

From the viewpoint of material mechanics, it is possible to suppress thetight fit section 22 from widening outward in the radial direction dueto the centrifugal force during rotation, by satisfying the expression(2). Thus, by satisfying the expression (2), the contact pressure of thetight fit section 22 can be maintained, and it is possible to suppressthe deviation between the impeller 10 and the shaft 5.

A groove portion 18 is provided inside the rear side surface 12 b of thedisc 12 in the radial direction so as to surround the tight fit section22. The groove portion 18 is formed by denting the rear side surface 12b of the disc 12 so as to follow the front side surface 12 a on theentire periphery of the tight fit section 22 (hub 20). In this manner,by providing the groove portion 18, it is possible to remove the thickportion of the disc 12 so that the thickness of the tight fit section 22becomes T1 in the axial range in which the tight fit section 22 isprovided, and thereby reduce the thickness of the tight fit section 22.Furthermore, by providing the groove portion 18, the thicknessdifference of each portion of the disc 12 is reduced, and for example,when enhancing the strength of the disc 12 by quenching, annealing orthe like, the heat treatment of the entire disc 12 can be evenlyperformed.

A loose fit section 24 is provided on the front side (the left side ofFIG. 2) of the tight fit section 22. That is, the loose fit section 24is provided on the front end side of the hub 20 compared to the tightfit section 22. An internal radius of the loose fit section 24 is set tobe slightly greater than the internal radius R of the tight fit section22. The internal radius of the loose fit section 24 is set to beslightly greater than the radius of the shaft 5. Thus, there is aclearance between an inner circumferential surface 24 a of the loose fitsection 24 and an outer circumferential surface 5 a of the shaft 5. Inaddition, the internal radius of the loose fit section 24 may be set tobe smaller than the radius of the shaft 5. In this case, the loose fitsection 24 is fitted into the shaft 5 by a smaller tightening allowancethan the tight fit section 22.

A plurality of blades 14 are provided on the front side surface 12 a ofthe disc 12. For example, these blades 14 are plate-like members made ofprecipitation hardening stainless steel, like a disc. Each of the blades14 has a constant plate thickness (blade thickness). The plurality ofblades 14 are arranged in the circumferential direction of the disc 12at predetermined intervals, and are provided approximately radially whenviewed from the axial direction. Furthermore, each of the blades 14stands up so as to be approximately perpendicular to the front sidesurface 12 a of the disc 12.

For example, the blades 14 are joined to the front side surface 12 a ofthe disc 12 by fillet welding or the like.

The cover 16 is provided on the front sides of the blades 14. Asillustrated in FIG. 2, the cover 16 is a substantially circularplate-like member when viewed in a planar view. Furthermore, the cover16 is curved and formed so as to follow the shape of the blade 14 in aside view when viewed from the cross section in the radial direction,and the front side surface 12 a of the disc 12. The cover 16 is fixed tothe front side front end of each blade 14, for example, by filletwelding or the like to suppress the vibration of each blade 14.

(Effect of First Embodiment)

In the present embodiment, the blades 14 are provided on the front sidesurface 12 a (surface) of the disc 12, and a part of the hub 20 fittedinto the shaft 5 is provided so as to protrude to the rear side withrespect to the rear side surface 12 b (rear surface) of the disc 12. Forthis reason, when the blades 14 are mounted on the front side surface 12a of the disc 12, the hub 20 is not obstructive. Thus, it is possible toprovide the rotary machine 1 having satisfactory workability duringmanufacturing.

Furthermore, in PTL 1, since the sleeve portion fitted into the shaft isplaced so as to be separated from the disc on which the center of thehalf section of the impeller is placed, there is a structure in whichthe sleeve portion easily widened outward in the radial direction.However, according to the present invention, the hub 20 is formed sothat a part thereof projects from the rear side surface 12 b of the disc12, and the tight fit section 22 having the great tightening allowanceis provided from the rear side to the front side. That is, since the hub20 is provided near the center of the half section of the impeller 10,and the tight fit section 22 provided in the hub 20 is fixedly fittedinto the shaft 5, it is possible to suppress the deviation between theimpeller 10 and the shaft 5 at the time of rotation.

Furthermore, according to the present embodiment, by providing the tightfit section 22 over the front side with respect to the rear side surface12 b of the disc 12, the tight fit section 22 can be provided at aposition closer to the center of the half section of the impeller 10.Thus, it is possible to suppress the deviation between the impeller 10and the shaft 5 at the time of rotation.

Furthermore, according to the present embodiment, by providing thegroove portion 18 in a region in which the disc 12 overlaps the range inwhich the tight fit section 22 are provided in the axial direction, thatis, near the tight fit section 22, it is possible to suppress the tightfit section 22 from widening outward in the radial direction due to thecentrifugal force at the time of rotation, and the contact pressure ofthe tight fit section 22 can be maintained. Thus, it is possible toreliably suppress the deviation between the impeller 10 and the shaft 5at the time of rotation.

In addition, since the thick portion of the disc 12 can be removed byproviding the groove portion 18, and the thickness difference of eachportion of the disc 12 can be reduced, for example, when enhancing thestrength of the disc 12 by quenching, annealing or the like, the heattreatment of the entire disc 12 can be evenly performed. Thus, it ispossible to provide a rotary machine 1 having high performance andexcellent strength.

(Rotary Machine of Second Embodiment)

Next, the rotary machine 1 of the second embodiment will be described.

FIG. 4 is an explanatory view of the rotary machine 1 of the secondembodiment.

In the first embodiment, in order to simplify the description, therotary machine 1 in which one impeller 10 is provided in the shaft 5 isdescribed. However, the second embodiment differs from the firstembodiment in that a plurality (two in FIG. 4) of impellers 10 areprovided in the shaft 5, shapes of the tight fit section 22 and theloose fit section 24 are different, and a sleeve 30 configured todistribute the gas G is provided.

Furthermore, for example, the rotary machine 1 of the second embodimentassumes a case in which the reduction in the length of the tight fitsection 22 is required depending on the circumstances of the layout ofthe impeller 10 compared to the first embodiment. In addition, adetailed description of the same configuration portions as the firstembodiment will be omitted here.

In the rotary machine 1 of the present embodiment, a plurality ofimpellers 10 is provided in series in the shaft 5. Moreover, the sleeve30 is provided between the rear side surface 12 b of the one disc 12 andthe front side surface 12 a of another disc adjacent to each other.

(Disc)

The tight fit section 22 has a thickness T2 in the radial direction, andis provided to have a length L2 from the rear side to the front side.Furthermore, a first tapered portion 23 a is provided in the rear end 23of the tight fit section 22. The first tapered portion 23 a is formed ina substantially tapered shape in which the rear end thereof graduallywidens from the rear side toward the front side (from the right side tothe left side in FIG. 4).

Furthermore, in the rotary machine 1 of the second embodiment, forexample, by the circumstances such as the layout, the tight fit section22 is shortened compared to the first embodiment. That is, arelationship between the length L1 of the tight fit section 22 in thefirst embodiment and the length L2 of the tight fit section 22 in thesecond embodiment is L2<L1.

In addition, in the rotary machine 1 of the second embodiment, in orderto supplement the reduction of the contact pressure of the tight fitsection 22 when fitting the shaft 5 due to the reduction of the tightfit section 22, the thickness of the tight fit section 22 is increasedcompared to the first embodiment. That is, a relationship between thethickness T1 of the tight fit section 22 in the first embodiment and thethickness T2 of the tight fit section 22 in the second embodiment isT2>T1.

Herein, the length L2 of the tight fit section 22, the thickness T2 ofthe tight fit section 22, and the internal radius R of the tight fitsection 22 are set so as to satisfy the following expression (3).

[Expression 3]

L2/√{square root over (RT2)}<0.8˜0.9  (3)

Herein, there is a possibility of the thick portion of the tight fitsection 22 being pulled outward in the radial direction due to thecentrifugal force at the time of rotation, and the tight fit section 22widening.

However, from the viewpoint of the material mechanics, it is possible tosuppress the tight fit section 22 from widening due to the centrifugalforce by satisfying the expression (3).

In the present embodiment, since the length L2 of the tight fit section22, the thickness T2 of the tight fit section 22, and the internalradius of the tight fit section 22 are set so as to satisfy theexpression (3), it is possible to suppress the tight fit section 22 fromwidening due to the centrifugal force. Thus it is possible to suppressthe deviation between the impeller 10 and the shaft 5 at the time ofrotation.

Furthermore, a convex portion 25 a is provided in the front end 25 ofthe loose fit section 24. The convex portion 25 a is formed inapproximately a V shape having a top portion on the front side whenviewed from the cross section in the radial direction. The convexportion 25 a is fitted into a concave portion 32 a provided in thesleeve 30 as will be described later. In addition, the shape of theconvex portion 25 a is not limited to the shape of the presentembodiment, and may be, for example, an approximately rectangular shapewhen viewed from the cross-section in the radial direction.

(Sleeve)

A sleeve 30 is provided between one disc 12 and another disc 12 adjacentthereto. In addition, in the above-mentioned PTL 1, although the sleeveand the disc are integrally formed, the sleeve 30 of the presentembodiment is provided as a separate component from the disc 12.

For example, the sleeve 30 is a member having an approximatelycylindrical shape and being made of precipitation hardening stainlesssteel same as a disc. For example, the sleeve 30 is formed by cuttingand then machining a seamless steel pipe. An internal diameter of thesleeve 30 is set to be slightly smaller than an external diameter of theshaft 5, and is fitted and fixed to the shaft 5 by shrinkage-fitting orthe like. Furthermore, an external diameter of the sleeve 30 is set tobe substantially the same as an external diameter of the loose fitsection 24 of the disc 12.

The sleeve 30 is placed on the upstream side of the gas G (see FIG. 1)flowing in the impeller 10, that is, on the front side of the disc 12.The sleeve 30 distributes the gas G flowing in between the blades 14,and effectively guides the gas G.

A second tapered portion 34 a is provided in the front end 34 of thesleeve 30. The second tapered portion 34 a is formed in a shapecorresponding to the first tapered portion 23 a provided in the rear end23 of the tight fit section 22. Specifically, the second tapered portion34 a is formed in an approximately tapered shape in which the front endthereof gradually widens from the rear side toward the front side (fromthe right to the left side in FIG. 4).

Furthermore, a concave portion 32 a is provided in the rear end 32 ofthe sleeve 30. The concave portion 32 a is formed in a shapecorresponding to the convex portion 25 a provided in the front end 25 ofthe loose fit section 24.

Specifically, the concave portion 32 a is formed in approximately a Vshape in which the front side thereof becomes a bottom when viewed fromthe cross section in the radial direction.

The sleeve 30 formed in this manner is placed between the rear sidesurface 12 b of one disc 12 and the front side surface 12 a of the otherdisc adjacent thereto. That is, the sleeve 30 is placed between the rearend of the hub 20 of one impeller 10 and the front end of the hub 20 ofthe other impeller 10 adjacent thereto.

At this time, the sleeve 30 is placed in a state in which the secondtapered portion 34 a of the sleeve 30 is brought into contact with thefirst tapered portion 23 a of the disc 12. In addition, the sleeve 30 isplaced in a state in which the convex portion 25 a of the disc 12 isfitted into the concave portion 32 a of the sleeve 30.

(Function)

When the rotary machine 1 is driven to rotate the impeller 10 mounted onthe shaft 5, the hub 20 of the disc 12 is pulled outward in the radialdirection due to the centrifugal force. For this reason, forceattempting to widen outward in the radial direction works on the tightfit section 22 and the loose fit section 24.

However, the sleeve 30 is placed in the state in which the secondtapered portion 34 a and the first tapered portion 23 a are brought intocontact with each other. Thus, the second tapered portion 34 a pressesthe first tapered portion 23 a from the outside in the radial direction,restricts the movement of the tight fit section 22 due to thecentrifugal force, and suppresses the tight fit section 22 from wideningoutward in the radial direction.

Furthermore, the sleeve 30 is placed in the state in which the concaveportion 32 a of the sleeve 30 and the convex portion 25 a of the disc 12are fit into each other. Thus, the concave portion 32 a of the sleeve 30restricts the movement of the loose fit section 24 due to thecentrifugal force, and suppresses the loose fit section 24 from wideningoutward in the radial direction.

(Effect of Second Embodiment)

For example, in some cases, shortening of the length of the tight fitsection 22 may be required depending on the circumstances such as thelayout of the impeller 10. In this case, in order to supplement thereduction of the contact pressure due to shortening of the tight fitsection 22, there is a need to increase the thickness of the tight fitsection 22. However, when the thickness of the tight fit section 22 isincreased, there is a risk of the thick portion being pulled outward inthe radial direction due to the centrifugal force, the tight fit section22 widening outward in the radial direction, and deviation between theimpeller 10 and the shaft 5 being generated.

However, according to the present embodiment, by providing the firsttapered portion 23 a in the rear end 23 of the tight fit section 22 ofthe hub 20, it is possible to suppress the tight fit section 22 fromwidening outward in the radial direction due to the centrifugal force.Accordingly, by providing the first tapered portion 23 a, it is possibleto shorten the length of the tight fit section 22 and provide a smallimpeller 10, while reliably suppressing the deviation between theimpeller 10 and the shaft 5 at the time of rotation.

Furthermore, according to the present embodiment, by placing the sleeve30 on the front side of the disc 12 which is the upstream of theinflowing gas G, the gas G can be effectively guided. In addition, byindividually providing the disc 12 and the sleeve 30, after joining theblades 14, the cover 16 or the like to the front side surface 12 a ofthe disc 12 by welding or the like, the sleeve 30 can be placed on thefront side of the disc 12. Accordingly, when the blades 14 or the likeare joined to the front side surface 12 a of the disc 12, the sleeve 30is not obstructive. Thus, it is possible to provide the rotary machine 1having the excellent workability at the time of manufacturing.

Furthermore, according to the present embodiment, since the secondtapered portion 34 a having the shape corresponding to the first taperedportion 23 a is provided on the front end 34 of the sleeve 30, thesleeve 30 can be placed in the state in which the second tapered portion34 a is brought into contact with the first tapered portion 23 a.Thereby, since the second tapered portion 34 a is able to press thefirst tapered portion 23 a from the outside in the radial direction, itis possible to suppress the tight fit section 22 from widening outwardin the radial direction due to the centrifugal force. Thus, it ispossible to reliably suppress the deviation between the impeller 10 andthe shaft 5 at the time of rotation.

Furthermore, according to the present embodiment, the concave portion 32a is provided in the rear end 32 of the sleeve 30, and the convexportion 25 a corresponding to the concave portion 32 a is provided inthe front end 25 of the loose fit section 24 of the hub 20. Thereby,since it is possible to fit the rear end 32 of the sleeve 30 and theloose fit section 24 by concavity and convexity, it is possible torestrict the movement of the loose fit section 24 by the sleeve 30, andit is possible to suppress the loose fit section 24 from wideningoutward in the radial direction due to the centrifugal force.Accordingly, it is possible to reliably suppress the deviation betweenthe impeller 10 and the shaft 5 at the time of rotation.

(Rotary Machine of Third Embodiment)

Next, the rotary machine 1 of the third embodiment will be described.

FIG. 5 is an explanatory view of the rotary machine 1 of the thirdembodiment.

In the first embodiment and the second embodiment, the tight fit section22 is provided over the front side with respect to the rear side surface12 b of the disc 12 from the rear side of the disc 12. However, thethird embodiment differs from the first embodiment and the secondembodiment in that the tight fit section 22 is provided in the rangeseparated from the rear side surface 12 b of the disc 12. In addition, adetailed description of the same configuration portions as those of thefirst embodiment and the second embodiment will be omitted here.

(Disc)

The hub 20 fitted into the shaft 5 is provided inside the disc 12 in theradial direction. A part of the hub 20 protrudes from the rear sidesurface 12 b of the disc 12 and is a through hole that penetratesthrough the front side and the rear side of the disc 12. Furthermore,the hub 20 has the tight fit section 22 provided on the rear side, theloose fit section 24 provided on the front side, and an intermediatesection 27 provided between the tight fit section 22 and the loose fitsection 24.

The tight fit section 22 has a thickness T3 in the radial direction, anda length L3 from the rear side to the front side (in the axialdirection).

Furthermore, the intermediate section 27 is provided between the tightfit section 22 and the loose fit section 24. The intermediate section 27has the same thickness T3 as the tight fit section 22, and is providedon the front side of the tight fit section 22 by the length C.

The internal radius of the intermediate section 27 is set so as to beapproximately equal to the internal radius of the tight fit section 22or smaller than the radius of the shaft 15, and slightly greater thanthe internal radius of the tight fit section 22. That is, the tighteningallowance of the intermediate section 27 when fitted into the shaft 5 isset so as to be approximately equal to the tightening allowance of thetight fit section 22, or slightly smaller than the tightening allowanceof the tight fit section 22.

Herein, the length L3 of the tight fit section 22, the thickness T3 ofthe tight fit section 22, and the internal radius R of the tight fitsection 22 are set so as to satisfy the following expression (4).

In addition, the length C of the intermediate section 27, the thicknessT3 of the intermediate section 27, and an internal radius R of theintermediate section 27 are set so as to satisfy the followingexpression (5).

[Expression 4]

L3/√{square root over (RT3)}≧0.8˜0.9  (4)

From the viewpoint of the material mechanics, by satisfying theexpression (4), it is possible to suppress the tight fit section 22 fromwidening outward in the radial direction due to the centrifugal force atthe time of rotation, and the contact pressure of the tight fit section22 can be maintained. Thus, it is possible to reliably suppress thedeviation between the impeller 10 and the shaft 5 at the time ofrotation.

[Expression 5]

C/√{square root over (RT3)}≧0.8˜0.9  (5)

From the viewpoint of the material mechanics, by satisfying theexpression (5), even when force widening outward in the radial directionworks due to the centrifugal force of the disc 12 at the time ofrotation, the intermediate section 27 bends. Thus, the transmission ofthe influence due to the centrifugal force to the tight fit section 22is suppressed, and widening of the tight fit section 22 to the outsidein the radial direction is suppressed.

(Effect of Third Embodiment)

According to the present embodiment, by providing the intermediatesection 27 in the length C between the tight fit section 22 and theloose fit section 24, the tight fit section 22 is fitted into the shaft5 in the range separated from the rear side surface 12 b of the disc 12.Thereby, the intermediate section 27 bends, and the influence due to thecentrifugal force of the disc 12 can be relaxed. Thus, since it ispossible to suppress the tight fit section 22 from widening outward inthe radial direction due to the centrifugal force, it is possible tosuppress the deviation between the impeller 10 and the shaft 5 at thetime of rotation.

In addition, the present invention is not limited to the above-mentionedembodiments.

In each embodiment, a case in which the rotary machine 1 is applied tothe centrifugal compressor 100 is described as an example.

However, the present invention is not limited thereto, and for example,the rotary machine 1 of the present invention can also be applied to adiagonal flow type compressor.

Furthermore, the rotary machine 1 of the present invention can also beapplied to, for example, a blower, without being limited to thecompressor.

Furthermore, in the rotary machine 1 of each embodiment, the presentinvention is applied to a closed impeller in which the cover 16 isprovided on the front side of the blade 14. However, the presentinvention is not limited thereto, and the present invention can also beapplied to an open impeller in which the cover 16 is not provided on thefront side of the blade 14.

Furthermore, in the rotary machine 1 of each embodiment, a part of thehub 20 is formed so as to protrude from the rear side surface 12 b ofthe disc 12. However, the lengths L1, L2 and L3 by which the hub 20 isprovided are design items that are suitably set by the radius R of theshaft 5, and the thicknesses T1 and T2 of the tight fit section 22.Thus, the hub 20 may not protrude from the rear side surface 12 b of thedisc 12.

Furthermore, in the rotary machine 1 of each embodiment, the disc 12 isfitted into the shaft 5 by shrinkage-fitting. Furthermore, in the rotarymachine 1 of the second embodiment, the sleeve 30 is fitted into theshaft 5 by shrinkage-fitting. However, the fitting method of the disc 12and the sleeve 30 with respect to the shaft 5 is not limited toshrinkage-fitting, and, for example, the disc 12 may be fitted into theshaft 5 by pressure-fitting.

Furthermore, in the rotary machine 1 of the second embodiment, theconvex portion 25 a is provided on the front end 25 of the loose fitsection 24, the concave portion 32 a is provided on the rear end 32 ofthe sleeve 30, and the loose fit section 24 and the sleeve 30 are fittedinto each other by concavity and convexity. However, the concave portionmay be provided on the front end 25 of the loose fit section 24, theconvex portion may be provided on the rear end 32 of the sleeve 30, andthe loose fit section 24 and the sleeve 30 may be fitted into each otherby concavity and convexity.

Furthermore, in the rotary machine 1 of the second embodiment, byfitting the loose fit section 24 and the sleeve 30 to each other byconcavity and convexity, the movement of the loose fit section 24 due tothe centrifugal force during rotation is restricted. However, forexample, the third tapered portion having the internal radius graduallyreducing toward the front end of the sleeve may be provided on the rearend 32 of the sleeve, and the fourth tapered portion having the externalradius gradually reducing toward the front end of the hub 20 may beprovided on the front end 25 of the loose fit section 24 of the hub 20so as to be matched with the shape of the third tapered portion.

By placing the sleeve 30 so as to bring the third tapered portion andthe fourth tapered portion into contact with each other, the loose fitsection 24 can be pressed from the outside in the radial direction.Thus, like the second embodiment, the movement of the loose fit section24 can be restricted, and it is possible to suppress the loose fitsection 24 from widening outward in the radial direction due to thecentrifugal force at the time of rotation.

INDUSTRIAL APPLICABILITY

According to the rotary machine of the present invention, when mountingthe blades on the surface of the disc, the hub is not obstructive, andthe workability during manufacturing is satisfactory.

Furthermore, according to the rotary machine of the present invention,the tight fit section provided in the hub of the impeller is fixedlyfitted into the shaft, it is possible to prevent the tight fit sectionfrom widening due to the centrifugal force at the time of rotation, andit is possible to reliably suppress the deviation between the impellerand the shaft.

REFERENCE SIGNS LIST

-   1 rotary machine-   5 shaft-   5 a outer circumferential surface (circumferential surface)-   10 impeller-   12 disc-   12 a front side surface (one side surface, surface)-   12 b rear side surface (the other side surface, rear surface)-   14 blade-   18 groove portion-   20 hub-   22 tight fit section-   23 a first tapered portion-   24 loose fit section-   25 a convex portion-   27 intermediate section-   30 sleeve-   32 a concave portion-   34 a second tapered portion

1-9. (canceled)
 10. A rotary machine comprising: a shaft that rotates; adisc that has a hub fitted into the shaft and is extended with theincreasing distance toward outward in a radial direction from a frontend to a rear end of the hub; and an impeller having a plurality ofblades provided on a surface of the disc, wherein a rear surface of thedisc is formed with a groove portion which is recessed from the rear endtoward the front end so as to surround the hub, and the groove portionis continuously formed to the rear end of the hub from the rear surfaceof the middle of the disc.
 11. The rotary machine according to claim 10,wherein the hub comprises a tight fit section, and the tight fit sectionis configured to be fitted to the shaft having an fastening margintherebetween.
 12. The rotary machine according to claim 10, wherein thegroove portion protrudes to the front end side than the position of therear-most end of the disc, in the axial direction of the shaft.
 13. Therotary machine according to claim 11, wherein the tight fit section isconfigured such that an fastening force is increased by a rotation ofthe shaft.
 14. The rotary machine according to claim 10, wherein in thestate in which the shaft is rotated, the rear end of the hub tilts, anda tight fit section is fixed to the shaft.